I assume Biden steps in if Obama is not Pres? (no matter what I dont think O will be denied Presidency)
Probably, if it's after the inauguration. Although it might not last long if it's determined that fraud occurred, then Biden's election as VP might be invalid as well. If it occurred before Thursdays electoral vote count, then at most Biden would act as President, if the House could not or did not pick a President from the others who got electoral votes. That is *supposed* to be just McCain, but it's also possible, even likely, that one of the Dem (Obama) electors voted for some other Dem, such as Hillary. That would mean that the House could choose that other Dem, and they likely would, rather than McCain.
If it should occur between January 8 and January 20th, I haven't a clue how it would go. He couldn't be impeached, because he would not yet be President. He could never be President, and likely only the Supreme Court could order that he not be inaugurated, in which case he would "not have qualified", and Biden would act as President until someone did, probably by the House picking them.
But in any event, any time after next Thursday, and it makes a Smell of a Hess.